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Periodic patterns and technique to control misalignment between two layers

  • US 9,835,447 B2
  • Filed: 10/24/2016
  • Issued: 12/05/2017
  • Est. Priority Date: 04/10/2001
  • Status: Expired due to Term
First Claim
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1. An apparatus for determining the relative positions between two layers of a device and at least one of the layers of such device, the two layers comprising:

  • a first periodic structure in a first layer of the device; and

    a second periodic structure having a first and second portion in a second layer of the device,wherein the first portion of the second periodic structure is overlying or interlacing with the first periodic structure and together are arranged for measuring the relative positions between the first and second layers of the device,wherein the second portion of the second periodic structure is in a region for measuring the second portion, and the first periodic structure does not extend into such region,the apparatus comprising;

    a source for illuminating the first periodic structure and the first portion of the second periodic structure that are overlying or interlacing with incident radiation and illuminating the second portion of the second periodic structure with incident radiation;

    at least one detector for detecting diffracted radiation from the illuminated first periodic structure and the first portion of the second periodic structure along two different detection paths to provide at least one first output signal, wherein positive first-order diffraction is directed along one of the two paths and negative first-order diffraction is directed along the other one of the two different detector paths, wherein the at least one detector is also configured to detect radiation from the illuminated second portion of the second periodic structure to provide a second output signal; and

    a processor for determining misalignment between the first and second periodic structures from the at least one first output signal and measuring the second portion of the second periodic structure based on the second output signal.

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